1. Field of the Invention
The present invention relates to an overhead image-reading apparatus, an image processing method, and a computer program product.
2. Description of the Related Art
Some conventional overhead image-reading apparatuses using one-dimensional image sensors correct distortion in the main-scanning direction of images.
For example, JP-A-2000-32232 discloses an image scanner including a one-dimensional image sensor that main-scans a document to be read and acquires a partial image and a sub-scanning mechanism that changes a read image of the document to be read entering the one-dimensional image sensor by rotating a reflecting mirror, and a technique in which images obtained by the main-scanning are converted based on change of an optical path length from the document to be read to the one-dimensional image sensor.
In some other overhead image-reading apparatuses, the following techniques are disclosed: a technique that corrects barrel-shaped distortion, which is distortion in the main-scanning direction, based on image and sensor information, a technique that corrects the barrel-shaped distortion based on a result of various image analyses performed for image correction, and a technique that corrects the barrel-shaped distortion by using a particular optical system generating no distortion.
The conventional overhead image-reading apparatus, such as the apparatus disclosed in JP-A-2000-32232, however, requires an X-coordinate conversion table, for example, for each reading target line. As a result, a data amount may increase. In addition, in the conventional overhead image-reading apparatus, image quality may deteriorate due to nearest-neighbor interpolation employed for image magnification, for example.